linux-kernel - Re: [PATCH] rust: Add #[must_use] to Lock::try_lock, GlobalLock::try_lock, and XArray::try

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Message-ID: <CANiq72n8qdymDJnqtvFqoOsFXJqn1EuvRqBkT+A_ibZmmh7SYw@mail.gmail.com>
Date: Fri, 18 Jul 2025 19:59:57 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: TruongSinh Tran-Nguyen <i@...ongsinh.pro>, Jason Devers <dev.json2@...il.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	ojeda@...nel.org, alex.gaynor@...il.com, gary@...yguo.net, 
	bjorn3_gh@...tonmail.com, lossin@...nel.org, a.hindborg@...nel.org, 
	aliceryhl@...gle.com, tmgross@...ch.edu, dakr@...nel.org
Subject: Re: [PATCH] rust: Add #[must_use] to Lock::try_lock,
 GlobalLock::try_lock, and XArray::try_lock

On Fri, Jul 18, 2025 at 4:20 PM TruongSinh Tran-Nguyen <i@...ongsinh.pro> wrote:
>
> This addresses issue #1133 in the rust-for-linux project.

We typically use the "Suggested-by:" and "Links:" tags for this,
please see e.g. how it was done in the patch linked below.

> diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
> index e82fa5be289c..1c2ddade6d6d 100644
> --- a/rust/kernel/sync/lock.rs
> +++ b/rust/kernel/sync/lock.rs
> @@ -175,6 +175,7 @@ pub fn lock(&self) -> Guard<'_, T, B> {
>      /// Tries to acquire the lock.
>      ///
>      /// Returns a guard that can be used to access the data protected by the lock if successful.
> +    #[must_use = "the lock unlocks immediately when the guard is unused"]
>      pub fn try_lock(&self) -> Option<Guard<'_, T, B>> {
>          // SAFETY: The constructor of the type calls `init`, so the existence of the object proves
>          // that `init` was called.

This part was done at:

    https://lore.kernel.org/rust-for-linux/20241212154753.139563-1-dev.json2@gmail.com/

which is soon landing in mainline.

We may want to add the comment on top here like in that patch to the
other 2, and possibly make the "reason string" after the `=` the same
one too.

Thanks for the patch!

Cheers,
Miguel